The present invention relates generally to automatic transmission systems and, more particularly, to a method of sealing the low/reverse gear fluid circuit within an automatic transmission case utilizing a grommet seal in combination with a steel shim in place of an original equipment manufacture (hereinafter xe2x80x9cOEMxe2x80x9d) gasket.
A common service complaint in Chrysler A604 (40TE, 41TE) automatic transmissions (hereinafter xe2x80x9cChrysler transmissions) involves a poorly functioning and/or worn out low/reverse clutch resulting from automatic transmission fluid (hereinafter xe2x80x9cATFxe2x80x9d) leakage in the low/reverse piston fluid circuit. Such fluid leakage is problematic in the aforementioned Chrysler transmissions because of the design of the low/reverse piston retainer. Instead of being machined into the transmission case as in previous automatic transmission designs, the low/reverse piston retainer is a stamped steel construction that is mounted on the interior surface of the transmission case being spaced apart therefrom by a relatively thin, flexible gasket. As a result the piston retainer has a tendency to distort due to its thin-walled construction even when the machine bolts, which secure it to the transmission case, are applied with the specified torque (i.e. 40 inch/pounds) against the flexible gasket. Thus, the OEM gasket, which is intended to seal an ATF feed passage extending through the piston retainer and gasket and into the transmission case, is insufficient to maintain the integrity of this fluid circuit and results in ATF leakage at the mating surfaces thereof.
One example of a prior art invention that attempts to remedy this problem is shown in U.S. Pat. No. 5,619,888 to Anthony which discloses a reinforcement member for a piston retainer in the form of an arcuate plate for installation within the piston retainer adjacent the A1xc2x0 F. feed passage. Although the arcuate reinforcement member provides for increased pressure and surface area for contacting the fluid actuator adjacent the ATF feed passage, it does not extend completely around the surface of the piston retainer. This technique still requires compression of the gasket material to seal around the ATF feed passage, which is the root cause of the leakage. Thus, distortion of the sheet metal piston retainer and subsequent fluid leakage can still occur.
Accordingly, the present invention has been developed to resolve this problem and other shortcomings of the prior art.
The present invention provides a repair method and apparatus comprising a fluorocarbon grommet seal for installation within the subject ATF feed passage in the transmission case in combination with a steel shim, which compresses the seal in position and maintains the integrity of the low/reverse piston fluid circuit. The steel shim functions as a spacer in substitution for the OEM gasket and also provides a non-compressible backing surface to prevent distortion of the piston retainer when installed.
Thus, by removing the OEM gasket from the interface of the piston retainer and the transmission case, the cause of the ATF leakage is eliminated.
Other features and technical advantages of the present invention will become apparent from a study of the following description and the accompanying drawings.